1. Field
The following description relates to technology that enables a second communication system to appropriately use all or a portion of radio resources that are allocated to a first communication system.
2. Description of Related Art
Much research is currently underway involving technologies that efficiently use limited frequency resources. Cognitive radio (“CR”) technology is in the spotlight.
In order to more efficiently use limited frequency resources, a “cognitive radio system,” or a “second communication system” using the cognitive radio technology may use frequency resources allocated to a “first communication system.”
For example, according to cognitive radio technology, a second base station or a second terminal that belongs to the second communication system recognizes all or a portion of at least one frequency resource allocated to the first communication system as an available frequency resource and performs a data communication using the recognized available frequency resource.
However, the first communication system has priority with respect to the available frequency resource. Accordingly, where a signal of the second communication system may collide with a signal of the first communication system, the second base station and the second terminal may need to stop the data communication or change a using frequency resource to another frequency resource.
The second base station or the second terminal may perform an “energy detection” or a “feature detection” for a received signal in order to determine whether the signal of the first communication system exists.